Re: Ternary operator patch

[JKB <bcs@...>]

Ryota,

With respect to your mods for if/then/else in an expression I appear to have
found a bug:

  b = 1
  local x, y = {aa=1, bb=2}, {aa=3.14, bb=2.718}
  a = if b == 1 then x else y
  print(a.aa)

prints 3.14 instead of 1. It produces the code:

       16      [8]     EQ              0 2 -2  ; - 1
       17      [8]     JMP             1       ; to 19
       18      [8]     JMP             0       ; to 19
       19      [8]     SETGLOBAL       1 -11   ; a


When I changed in ifexpr(...) two lines of luaK_exp2anyreg(...) to
luaK_exp2nextreg(...) it worked - as shown below:

static void ifexpr (LexState *ls, expdesc *v) {
  /* ifexpr -> IF cond THEN expr ELSE expr */
  FuncState *fs = ls->fs;
  int condexit;
  int escapelist = NO_JUMP;
  luaX_next(ls);        /* skip IF */
  condexit = cond(ls);        /* check cond */
  checknext(ls, TK_THEN);      /* skip THEN */
  expr(ls, v);          /* eval THEN part */
  luaK_exp2nextreg(fs, v);      /* set result to reg. */    
//!!!!!!!!!!!!!!!!!!!!!
  luaK_freeexp(fs, v);        /* free reg. bound to v */
  luaK_concat(fs, &escapelist, luaK_jump(fs));  /* JMP to last */
  luaK_patchtohere(fs, condexit);    /* label to JMP when cond is false */
  checknext(ls, TK_ELSE);      /* skip ELSE */
  expr(ls, v);          /* eval ELSE part */
  luaK_exp2nextreg(fs, v);      /* set result to reg. */     
//!!!!!!!!!!!!!!!!!!!!!
  luaK_patchtohere(fs, escapelist);    /* label to JMP when cond is true */
}

Do you see any problems?

JK Berkeley





--
Sent from: http://lua.2524044.n2.nabble.com/Lua-l-f2524044.html